The proposed research seeks to study the interaction of flagellar dynein with both flagellar and cytoplasmic microtubules in order to elucidate the mechanism by which their movements are generated and coordinated. Experiments will be conducted in which the polarity of microtubules within the mitotic apparatus will be examined using bound flagellar dynein to determine if antiparallel microtubules are adjacent to each other and, therefore, likely to interact. The polarity of microtubules in other systems such as psuedopodia and neurites will also be analyzed using dynein as a probe. In addition, the orientation of dynein arms with respect to intrinsic microtubule polarity will be determined by binding dynein to microtubules of known structural polarity. Studies will also be performed in which assembled microtubules cross-bridged by flagellar dynein will be examined for their ability to slide apart upon ATP addition. Sliding might be the mechanism by which cytoplasmic microtubules produce movements in vivo. Moreover, microtubules assembled in vitro from purified brain tubulin will be used as an affinity probe to select for a postulated mitotic dynein. If detected, this "dynein" will be examined to determine if it can induce ATP-dependent cross-bridging between microtubules. The affinity of dynein for particular microtubules or for specific sites on those microtubules will be studied. In addition, a stimulation of dynein's ATPase activity resulting from microtubule cross-bridging and a cooperative effect of dynein binding to microtubules will be considered with respect to the ability of microtubules to coordinate and regulate their movements.